Porphyrin-based photosensitizers for visible-light polymerization and antibacterial applications

Abstract

This study highlights the outstanding photo-initiating properties of two new visible-light absorbing benzophenone porphyrin-based photosensitizers (PBP and PBPZn) for the free-radical (FRP), cationic (CP) photopolymerization and thiol–ene reactions under visible LEDs exposure (405, 505 and 530 nm) under air or in laminate, and at low intensities. As confirmed by electronic paramagnetic resonance spin trapping (EPR ST) and Laser Flash Photolysis studies, both porphyrins play a dual role as electron donor molecule when combined with iodonium salt (Iod) and participate in a H-abstraction reaction in association with N-methyldiethanol amine (MDEA) or thiol derivatives (cysteamine or N-acetylcysteine). For the first time, interesting kinetic profiles for the polymerization of a bio-based monomer (SOA) are observed under blue and green-light irradiation. Notably, the 4-methylphenyl-, aminoalkyl- and thiyl radicals which are generated from the photolysis of porphyrin/Iod, porphyrin/MDEA and porphyrin/cysteamine (or N-acetylcysteine) respectively, can initiate the radical polymerization of SOA and very high FCs are observed; up to 90% under LED@405 nm and >60% under LED@530 nm exposure. Finally, PBPZn-based materials demonstrated photoactivable properties for antibacterial applications. Under visible-light irradiation, these materials can produce biocide reactive oxygen species (ROS) leading to a tremendous inhibition of S. aureus proliferation.